US model Caprice says she treats her two sons like twins and has given them the same birthday even though one of them was carried by a surrogate.

The boys, called Jax and Jett, made headlines when she gave birth just weeks after her surrogate, in 2013.

She told Hello! magazine that most people assume they are twins.

She said: "If anyone asks, are they twins? I always reply, yes.

"I need quite a long time to tell my story and they look so close in age it is easier to say they are twins."

Caprice, who fell pregnant only a matter of weeks after her surrogate did, said the boys will share a birthday. She said: "When it comes to their birthdays, I will find an official date and we'll celebrate on the same day. As they get older, it will be up to them if they prefer separate birthdays.

"So yes, I will tell them the truth eventually, but I don't think it will affect them in a bad way or make them feel any different. I love these boys so much, more than my own life, and I'm their biological mother."

The star, who is about to publish her autobiography My Boys, My Body, My Business, says her sons "interact like twins".

She said: "They adore each other but also drive one another mad. So they'll fight over ridiculous things like their cars or who gets on a swing first, yet if they're not together every moment they miss each other."